This invention relates to ultrasound medical imaging systems, and more particularly to real-time scan conversion methods in an ultrasound system.
Ultrasound medical imaging is the imaging of internal areas of a patient's body using ultrasound energy. Ultrasound energy is sound wave energy having a frequency greater than approximately 20 kHz. Ultrasound signals, typically of 2 MHz to 10 MHz, are transmitted into a patient's body via a transducer array. The signals are in-part absorbed, dispersed, refracted and reflected by the patient's body. Reflected ultrasound signals are received at transducer elements which convert the reflected ultrasound signals back into electronic signals. A received ultrasound beam-pattern is a product of the transmit beam-pattern and the reflected beam-pattern. The received beam-pattern typically is processed to analyze echo, doppler and flow information and obtain an image of the patient's encountered anatomy (e.g., tissue, flow, doppler).
Typically, ultrasound energy is directed in a sector scan of a patient area. In such instances, the received beam-pattern is a group of polar-coordinate vectors. As the display devices are raster cartesian-coordinate devices, the received data is converted into raster format. Such conversion is referred to as a scan conversion process. It also is known to direct ultrasound energy as a linear scan of a patient's area. In such case, the received beam-pattern is a group of cartesian-coordinate vectors. As the display devices are raster cartesian-coordinate devices, the received data is converted and/or scaled into a display raster cartesian-coordinate system. Such conversion/scaling also is referred to as a scan conversion process.
Scan conversion involves interpolation and scaling of vector data (e.g., polar or cartesian vectors) into raster data. A resulting set of raster data is used to define an ultrasound display image at a given moment in time. Multiple sets of raster data are used to (i) define the same image at different times, or (ii) add a third dimension to an image. Conventional ultrasound imaging systems allow display of an image as a sector area or a cartesian grid. The scan conversion process manipulates collected data to generate raster image data in a desired display format. It also is known to geometrically transform the vector data to zoom in on or rotate an image.
The classical scan conversion method is to work back from a raster point on the display. For a given raster point, an inverse transformation is performed to identify input vector samples in the vicinity of the raster point. As the collected input data is a set of vectors, the output raster point does not exactly coincide with a given input vector. Thus, nearby input vectors are identified, then the values for such vectors are interpolated to define a value at the raster point of interest. Such process is performed for each raster point on the display. As a result, the scan conversion process is computation intensive.
It is desirable to reduce computation overhead or otherwise increase efficiency in allocating system throughput for an ultrasound system. Accordingly, it is desirable to achieve an efficient scan conversion method.